Methods and systems for estimating residual useful life of a rolling element bearing

ABSTRACT

Estimating residual useful life of a rolling element bearing in an operating gas turbine engine is provided. A processor receives a vibration signal from a vibration sensor. The vibration signal includes a vibratory response of the rolling element bearing. Processor detects a vibratory pattern of the rolling element bearing from the vibration signal and compares the vibratory pattern to a reference vibratory pattern. Processor identifies a failure propagation stage in which the vibratory pattern matches the reference vibratory pattern. Processor correlates the failure propagation stage to the residual useful life remaining in the rolling element bearing and generates an output signal representing the residual useful life remaining in the rolling element bearing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, and claims priority to, and thebenefit of U.S. Non-Provisional application Ser. No. 14/879,981,entitled “METHODS AND SYSTEMS FOR ESTIMATING RESIDUAL USEFUL LIFE OF AROLLING ELEMENT BEARING,” filed on Oct. 9, 2015, is hereby incorporatedby reference in its entirety.

FIELD

The present disclosure relates to gas turbine engines, and morespecifically, to systems and methods for estimating the residual usefullife of a rolling element bearing.

BACKGROUND

Rolling element bearings, often used in rotor bearing systems of gasturbine engines for supporting rotating shafts, may be subjected tocyclical high loading forces, which may result in failure of the rollingelement bearings. A primary failure mode is bearing spall evidenced bythe release of particles from the failed rolling element bearing intothe lubricating system. Conventional methods for detecting spallinitiation in a rolling element bearing include detection of thepresence of particles by an oil debris monitoring system. As not everyspall progresses to failure within an expected period of time, thedetection of spall initiation cannot be a predictor of how far along therolling element bearing is in the failure progression process and whenthe imbalance response will occur with impending failure.

SUMMARY

A method is provided for estimating residual useful life of a rollingelement bearing in an operating gas turbine engine, according to variousembodiments. The method comprises receiving, by a processor, a vibrationsignal from a vibration sensor. The vibration signal includes avibratory response of the rolling element bearing. Processor detects avibratory pattern of the rolling element bearing from the vibrationsignal and compares the vibratory pattern to a reference vibratorypattern. Processor identifies the failure propagation stage in which thevibratory pattern matches the reference vibratory pattern. Processorcorrelates the failure propagation stage to the residual useful liferemaining in the rolling element bearing and generates an output signalrepresenting the residual useful life remaining in the rolling elementbearing.

A method is provided for estimating residual useful life of a rollingelement bearing of a rotor bearing system in an operating gas turbineengine, according to various embodiments. The method comprises receivingby a processor, a vibration signal from a vibration sensor of the rotorbearing system. The vibration signal includes a vibratory responseassociated with a vibratory pattern of the rolling element bearing.Processor determines relative contributions of an impulse response andan imbalance response in the vibratory response. The relativecontributions define a vibratory pattern. Processor determines a failurepropagation stage of the rolling element bearing from the vibratorypattern and correlates the failure propagation stage to the residualuseful life remaining in the rolling element bearing.

A system is provided for estimating residual useful life of a rollingelement bearing in an operating rotor bearing system, according tovarious embodiments. The system comprises a vibration monitoring systemincluding a processor for detecting a vibratory response of the rollingelement bearing by receiving a vibration signal representing thevibratory response. Processor is configured, in response thereto, todetect a vibratory pattern from the vibratory response and compare thevibratory pattern to a reference vibratory pattern. Processor identifiesthe failure propagation stage in which the vibratory pattern matches thereference vibratory pattern. Processor correlates the failurepropagation stage to the residual useful life remaining in the rollingelement bearing.

In any of the foregoing embodiments, detecting the vibratory patterncomprises measuring a vibration frequency and a vibration amplitude toobtain a measured vibration frequency and a measured vibrationamplitude. Detecting the vibratory pattern comprises detecting a changein the vibratory pattern. The vibratory pattern comprises a vibrationfrequency range and a vibration amplitude range and detecting the changein the vibratory pattern comprises detecting a shift in the vibrationfrequency range and a diminution in the vibration amplitude. Thereference vibratory pattern comprises a reference vibration frequencyrange and a reference vibration amplitude range, wherein comparing thevibratory pattern to the reference vibratory pattern comprises comparingthe measured vibration frequency against the reference vibrationfrequency range and the measured vibration amplitude against thereference vibration amplitude in the failure propagation stage.Comparing the vibratory pattern comprises comparing a spectral diagramof the vibratory pattern against a spectral diagram of the referencevibratory pattern in the failure propagation stage. A health score rangemay be assigned to the rolling element bearing within each failurepropagation stage. Assigning a health score range comprises determininga percentage of the vibration frequency and the vibration amplitudewithin the vibratory pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the drawing figures, wherein like numeralsdenote like elements.

FIG. 1A is a schematic representation of a rolling element bearingsupporting a shaft in a rotor bearing system including a vibrationsensor, according to various embodiments;

FIG. 1B is a schematic representation of the rolling element bearing ofFIG. 1A, according to various embodiments;

FIG. 2 is an exemplary spectral diagram of a spall progression of therolling element bearing such as depicted in FIG. 1, according to variousembodiments;

FIG. 3 is a system for estimating the residual useful life of therolling element bearing such as depicted in FIG. 1, according to variousembodiments;

FIG. 4 is a weighting diagram illustrating the respective contributionsof an impulse response and an imbalance response to the systems andmethods for estimating the residual useful life of the rolling elementbearing, according to various embodiments;

FIG. 5 is a graph illustrating energy contribution (y-axis) to thevibratory response along a time line (x-axis) and assignment ofexemplary health scores in the failure propagation stages, according tovarious embodiments; and

FIG. 6 is a flow diagram of a method for estimating the residual usefullife of the rolling element bearing such as depicted in FIG. 1,according to various embodiments.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration. While these exemplary embodiments are described insufficient detail to enable those skilled in the art to practice thepresent inventions, it should be understood that other embodiments maybe realized and that logical changes and adaptations in design andconstruction may be made in accordance with the present inventions andthe teachings herein. Thus, the detailed description herein is presentedfor purposes of illustration only and not of limitation. The scope ofthe present inventions is defined by the appended claims. For example,the steps recited in any of the method or process descriptions may beexecuted in any order and are not necessarily limited to the orderpresented. Furthermore, any reference to singular includes pluralembodiments, and any reference to more than one component or step mayinclude a singular embodiment or step. Also, any reference to attached,fixed, connected or the like may include permanent, removable,temporary, partial, full and/or any other possible attachment option.Additionally, any reference to without contact (or similar phrases) mayalso include reduced contact or minimal contact. Furthermore, anyreference to singular includes plural embodiments, and any reference tomore than one component or step may include a singular embodiment orstep.

Various embodiments are directed to systems and methods for estimatingthe residual useful life of a rolling element bearing in a rotor bearingsystem of an operating gas turbine engine. Various embodiments assesschanges in vibratory responses and patterns of the rolling elementbearing as spalling (failure) thereof progresses, providing informationas to how far along the rolling element bearing is toward failure andthe residual useful life remaining in the rolling element bearing. Avibratory response includes a ratio of an imbalance response to animpulse response. As used herein, the term “impulse response” refers toa response of the rolling element bearing to a very brief excitationcaused by a defect (e.g., spalling) on the rolling element bearing(i.e., on a bearing race or a ball thereof). The impulse response is theresponse obtained from exciting the rolling element bearing (and astationary housing thereof) and the rolling element bearing (and thestationary housing thereof) responding at its natural frequency (highfrequency (greater than, for example, 1000 kHz)). The term “imbalanceresponse” refers to the response of the entire rotor bearing system dueto the displacement of the rotor's center of mass from the center line.This displacement is evident every rotation of the rotor and hencecomprises the spin frequency of the rotor (e.g., low hundreds Hertz).The imbalance response is equal to the product of mass x eccentricity.Thus, the frequency range of the vibratory response identifies whetherthe vibratory response is more of an impulse response or an imbalanceresponse (i.e., the relative contributions of the impulse response andthe imbalance response).

Referring now to FIGS. 1A and 1B according to various embodiments, arotor bearing system 10 comprising a rolling element bearing 12supporting a shaft 14 in an operating gas turbine engine 16 is shown. Astationary housing encloses the rolling element bearing 12. The rotorbearing system 10 includes a vibration sensor 18 for monitoringvibration responses of the rotor bearing system 10. Changes in thevibration responses of the rotor bearing system 10 as spalling (a“bearing defect”) of the rolling element bearing 12 progresses are usedto estimate how close the rolling element bearing 12 is toward failureand the residual useful life remaining in the rolling element bearingaccording to various embodiments.

More specifically, the vibration sensor 18 sends a vibration signal to avibration monitoring system. The vibration signal represents thevibration response of the rolling element bearing in the rotor bearingsystem of the operating gas turbine engine. The vibration monitoringsystem may include a processor 400 that receives the vibration signaland in response thereto, is configured to detect vibratory patterns ofthe rotor element bearing 12 in rotor bearing system 10, includingchanges in the vibratory patterns as failure progresses. The vibratorypatterns comprise the vibratory response or a change in the vibratoryresponse. Vibration monitoring systems are well known to those skilledin the art and will not be described here in any detail. While theprocessor 400 may be included in the vibration monitoring system 300, itmay additionally or alternatively be separate therefrom. Broad bandvibration monitoring may be used, for example, using vibrationmonitoring implementing International Organization for Standardization(“ISO) ISO 10816, which is hereby incorporated by reference for anypurpose. Vibration measurements may be made in three directions(horizontal, vertical, axial). ISO 10816 keeps the lower frequency rangeflexible between 2 Hz and 10 Hz, depending on the machine type. Theupper frequency is 1000 Hz. ISO 10816 operates with the term vibrationamplitude, which, depending on the machine type, can be an RMS value ofvibration velocity, acceleration or displacement. For certain vibrationmonitoring machines, ISO 10816 also recognizes peak-to-peak values ascondition criteria.

Referring now to FIGS. 2 through 4, according to various embodiments,the stage of failure of the rolling element bearing in the rotor bearingsystem may be determined by assessing changes in vibratoryresponse/vibratory patterns of the rolling element bearing 12 asspalling (failure) progresses. The spectral vibratory response of spallprogression follows a predictable vibratory specific pattern as therolling element bearing 12 deteriorates to failure (see, e.g., thespectral diagram in FIG. 2). The rolling element bearing defect (thespalling) causes an impulse for every rotation of the shaft (for asingle point defect). As the rolling element bearing degrades ordeteriorates (spalls), the defect becomes more widespread causing theloss of centerline of the bearing and an increase in other vibrationfrequencies (broadband). As the fault progresses, the impulse responseamplitude is ‘drowned-out’ and the imbalance response dominates.

The time between spall initiation and rolling element bearing failure isdefined by successive failure propagation stages (referred to herein asStage 1 (21), Stage 2 (22), Stage 3 (23), and Stage 4 (24) as depictedin FIGS. 2 and 3. The vibratory specific patterns fall within the boundsof each failure propagation stage. FIG. 2 is an exemplary spectraldiagram of the successive failure propagation stages with exemplaryvibratory specific patterns within the bounds of each stage. FIG. 3depicts a weighting diagram of an impulse response (Impulse ResponseVibration Monitoring, also known as Advanced Vibration Monitoring(“Advanced Vibe”)) of the rotor bearing system and an imbalance response(Imbalance Response Vibration Monitoring, also known as ClassicalVibration Monitoring) in the different failure propagation stages. FIG.4 similarly depicts a weighting diagram between impulse response andimbalance response indicating the relative contributions thereof throughthe failure propagation stages. Still referring to FIGS. 2 through 4,spalling (deterioration) of the rolling element bearing 12 begins inStage 1. Impulse response vibration monitoring may detect spallinitiation, i.e., the beginning of bearing deterioration by detectinghigher vibration frequency utilizing an enveloping method as known toone skilled in the art at spall initiation relative to the vibrationfrequency in subsequent stages. Stage 1 is a pre-initiation stage. Thespectral diagram of FIG. 2 shows the highest impulse response withinStage 1 due to the defect (spall initiation). In Stage 1, the impulseresponse (contribution) to the vibratory response is higher than theimbalance response (see also, FIG. 3). The detection capability withinthis frequency range is hardware dependent. A vibration sensor notcapable of the associated high frequency range will not detect thevibratory response, and will falsely indicate a defect-free rollingelement bearing.

As deterioration progresses from Stage 1, the vibration responseparameters begin to change. For example, the dominant frequency range ofthe vibratory response starts to shift lower and the vibration amplitudebegins to diminish. As frequency shifts occur and the vibrationamplitude diminishes, an imbalance response is detected as hereinafterdescribed. Stage 2 is an initiation stage. The vibratory response due tothe bearing defect is detectable within a lower frequency range than inStage 1. Key defect feature indicators are determined by signaldemodulation from the structural resonance. In Stage 2, there is lessimpulse response relative to that in Stage 1 and more imbalance response(FIG. 3), i.e., the imbalance/impulse ratio is less than one.

Stage 3 is the stage in which the imbalance response is sensed by thevibration sensor. At this stage, the impulse response due to the bearingdefect is fully developed with detectable side lobes within the responsefrequency range. The detectible imbalance response is also apparent inStage 3. Impulse response limits (i.e., maximum amplitude as measured,for example, in inches per second) depends upon the vibratoryenvironment) are exceeded and the vibratory response is more of animbalance response. The relationship (i.e., weighting as depicted inFIGS. 3 and 4) between impulse response and imbalance response is usedin this stage to track the stage of failure and predict when Stage 4will be activated. Stage 3 is the transitional region (as measured bytime) between impulse response at high vibration frequency and imbalanceresponse). In Stage 3, the imbalance response/impulse response asmeasured in vibration amplitude is equal to one.

Stage 4 shows a definite change in vibratory response as evidenced bythe spectral diagram of FIG. 2. The imbalance response dominates thevibratory response (see also, FIGS. 3 and 4). The impulse response isgrowing but the imbalance response overshadows the overall energycontent. With an impulse response excursion, the ratio between theimpulse response and imbalance response is used for further damagepropagation assessment. At this stage, the imbalance/impulse ratio willexceed one, thereby signifying the dominant imbalance response. Withfurther damage propagation, it will be observed that the impulseresponse will spread across additional frequency range and imbalanceexciting other response includes with additional non-interval vibrationcomponents.

Referring now to FIG. 5, according to various embodiments, a healthscore may be assigned to the rolling element bearing as it progressesthrough the various failure propagation stages. For example, as depictedin FIG. 5, the rolling element bearing may be assigned a health score of0-3 when the rolling element bearing is in Stage 1, a health score of3-8 when in the transitional region, and a health score of 8-10 when inStage 4. Of course, the health scores may be any type of grading system,with the lower scores in Stage 4 rather than as shown by example in FIG.5. The assignment of the various health scores within a single stagewill be hereinafter described.

Referring now to FIG. 6, according to various embodiments, a method 100for estimating residual useful life of the rolling element bearingbegins by detecting the vibratory pattern of the rotor bearing system inan operating gas turbine engine (step 110). The vibratory patterncomprises the vibration frequency and the vibration amplitude. Detectingthe vibratory pattern comprises measuring the vibration frequency andthe vibration amplitude. As noted previously, a shift in the vibrationfrequency and diminution in the vibration amplitude indicates aprogression toward failure (i.e., progression along the trajectorytoward the imbalance response) from the impulse response.

The method 100 for estimating residual useful life of a rolling elementbearing in an operating gas turbine engine continues by comparing thevibratory pattern to a reference vibratory pattern (e.g., as determined,for example, by a spectral diagram such as shown in FIG. 2) in a failurepropagation stage of a plurality of successive failure propagationstages (Stage 1, Stage 2, Stage 3, and Stage 4) (step 120), i.e., themeasured real time vibration parameter (e.g., vibration frequency andvibration amplitude) is compared against a reference vibrationparameter. A deviation from the reference vibratory pattern indicatesprogression toward failure of the rolling element bearing. The methodfor estimating residual useful life of a rolling element bearing in anoperating gas turbine engine continues by identifying the failurepropagation stage in which the vibratory pattern substantially matchesthe reference vibratory pattern (step 130). As used herein, the term“substantially” in this context only means that the vibration frequencyand vibration amplitude are within the reference vibration frequency andvibration magnitude ranges of the particular stage. The particularranges depend on the vibrational environment.

The method for estimating residual useful life of a rolling elementbearing in an operating gas turbine engine continues by correlating thefailure propagation stage to the residual useful life remaining in therolling element bearing (step 140). For example, if the rolling elementbearing is determined to be in Stage 4, the residual useful life islimited (see, e.g., FIG. 5). However, the degree that the remaininguseful life is limited may further be determined by reference to thehealth score. In the depicted embodiment of FIG. 5, a health score of 8correlates to a longer residual useful life than a health score of 10.The health score of 8 relative to the health score of 10 in the depictedembodiment reflects percentages of the measured vibration frequencyrelative to the reference vibration frequency and the measured vibrationamplitude relative to the reference vibration amplitude. For example,the health score of 8 may represent a rolling element bearing 12 in astage where the reference vibration frequency is x and the referencevibration amplitude is y. In the depicted embodiment of FIG. 5, thecloser the measured vibration frequency and vibration amplitude is tothe high end of the respective range of each, the higher the healthscore. In the depicted embodiment of FIG. 5, that would translate to ashorter residual useful life.

A system 200 (FIG. 3) for estimating residual useful life of a rollingelement bearing in an operating rotor bearing system is also provided inaccordance with various embodiments. The system comprises the vibrationmonitoring system 300 for detecting a vibratory response of the rollingelement bearing and the rotor bearing system in an operating gas turbineengine. The vibration monitoring system may include the processor 400 orbe separate therefrom. The processor receives a vibration signalrepresenting the vibratory response from the vibration sensor 18 and isconfigured, in response thereto, to detect a vibratory pattern from thevibratory response. The processor is also configured to compare thevibratory pattern to a reference vibratory pattern in the failurepropagation stage of a plurality of successive failure propagationstages (Stage 1, Stage 2, Stage 3, and Stage 4 as previously described).The processor system is further configured to identify the failurepropagation stage in which the vibratory pattern matches the referencevibratory pattern, thereby determining the failure propagation stage ofthe rolling element bearing and correlate the failure propagation stageto the residual useful life remaining in the rolling element bearing.

While the present disclosure has been described with respect to rollingelement bearings of aircraft gas turbine engines, it is to be understoodthat various embodiments may provide benefits for rotor bearing systemsof automobiles and in other rolling element bearing applications.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the disclosure. The scope of the disclosure is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.”Moreover, where a phrase similar to “at least one of A, B, or C” is usedin the claims, it is intended that the phrase be interpreted to meanthat A alone may be present in an embodiment, B alone may be present inan embodiment, C alone may be present in an embodiment, or that anycombination of the elements A, B and C may be present in a singleembodiment; for example, A and B, A and C, B and C, or A and B and C.Different cross-hatching is used throughout the figures to denotedifferent parts but not necessarily to denote the same or differentmaterials.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment”, “an embodiment”,“various embodiments”, etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f) unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises”,“comprising”, or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

What is claimed is:
 1. A system for estimating residual useful life of arolling element bearing in an operating rotor bearing system, the systemcomprising: a vibration monitoring system including or in communicationwith a processor for detecting a vibratory response of the operatingrotor bearing system by receiving a vibration signal representing thevibratory response and configured, in response thereto, to: detect avibratory pattern from the vibratory response; compare the vibratorypattern to a reference vibratory pattern; identify a failure propagationstage in which the vibratory pattern matches the reference vibratorypattern; and correlate the failure propagation stage to the residualuseful life remaining in the rolling element bearing.
 2. The system ofclaim 1, wherein the processor detects a vibratory pattern from thevibratory response including a measurable vibration frequency and ameasurable vibration amplitude.
 3. The system of claim 1, wherein theprocessor detects a change in the vibratory pattern.
 4. The system ofclaim 1, wherein the vibratory pattern comprises a vibration frequencyrange and a vibration amplitude range and a change in the vibratorypattern comprises a shift in the vibration frequency range and adiminution in the vibration amplitude.
 5. The system of claim 1, whereinthe reference vibratory pattern comprises a reference vibrationfrequency range and a reference vibration amplitude range, wherein theprocessing system compares the measured vibration frequency against thereference vibration frequency range and the measured vibration amplitudeagainst the reference vibration amplitude in the failure propagationstage.